Bitter cold grips West

Tuesday

Jan 15, 2013 at 12:01 AM

As an unusual cold spell gripped parts of the West for a fifth day, some California citrus growers reported damage to crops, and an agriculture official said national prices on lettuce have started to rise because of lost produce in Arizona.

Staff and wire reports

As an unusual cold spell gripped parts of the West for a fifth day, some California citrus growers reported damage to crops, and an agriculture official said national prices on lettuce have started to rise because of lost produce in Arizona.

But in the northern San Joaquin County, industry experts said the cold is a good thing for many local crops.

In the southern San Joaquin Valley, where farmers are fighting to protect about $1.5 billion worth of citrus fruit on their trees, Sunday temperatures dropped to 25 degrees in some areas and stayed low longer than previous nights.

In San Joaquin County, where there is no substantial commercial citrus production, the frosty temperatures are more of a blessing than a bane, farm experts said.

Deciduous crops, such as cherries, grapes, almonds, apples and walnuts, actually require some amount of midwinter chill for optimum development.

"We'll take any and all cold that we can at this time of year to fulfill the chilling requirements of the trees," said Joe Grant, a farm adviser with the University of California Cooperative Extension in Stockton.

Proper chilling, which varies by tree species, puts the plant into a dormant state and sets it to respond to warmer spring and summer weather with a strong bloom and fruit or nut production.

"The good side of the story is we're catching up on the chilling hours, which will produce a good strong bud break and bloom for all the perennial crops," said Paul Verdegaal, a vineyard and almond adviser with UC Cooperative Extension.

A UC weather station near Lodi has recorded more than 700 hours of below-45-degree weather since Nov. 1.

With the overnight low a subfreezing 24 degrees at the National Weather Service station in Stockton early Monday, and even lower temperatures in other areas of the county, some crop damage may be seen.

"It may be hurting some younger trees and vines, but generally, things are in dormancy, so it's not too much of a problem," Verdegaal said.

Grant said walnuts, one of the crops he specializes in, are particularly susceptible.

"Especially when we get to the mid- to low 20s, we can start to see freeze damage to walnut trees," he said.

Any such damage, however, won't become evident until the trees begin to leaf out in the spring.

But prolonged temperatures in the mid-20s or below cause damage to citrus crops in the southern Valley.

"It was our coldest night to date," said Paul Story of Exeter-based California Citrus Mutual, an association of the state's 3,900 citrus growers. "I think mandarin growers are going to see a range of significant damage, enough that they will have to separate their crops."

Mandarins are more susceptible to cold than other citrus and start to freeze at about 32 degrees, Story said. Because many mandarin trees were planted in recent years as the fruit's popularity soared, they are grown in colder areas outside the traditional citrus belt.

Other citrus crops saw little or minimal damage, Story said. This year's high sugar content in oranges helped protect them, he said, because sugar inhibits freezing.

Growers deployed wind machines to keep the warm air closer to the ground and irrigation to raise the temperature in the groves. Rows farthest away from the protection could be damaged, Story said. And farmers who do not have wind machines could lose crops.

And farmers are on the hook for a fifth cold night: a freeze warning remains in effect until 10 a.m. today for Central California.

In Southern California, strong winds helped to keep crops out of danger by keeping the cold from settling.

Temperatures in downtown Los Angeles fell to 34 degrees, breaking the previous record of 36 degrees set on Jan. 14, 2007.

To the east, the freezing temperatures already have done enough damage to southwestern Arizona lettuce crops that prices are increasing, said Kurt Nolte, a Yuma, Ariz.-based agricultural agent for the University of Arizona.

The area provides much of the nation's leafy greens during the winter, and farmers are reporting damage to many romaine and iceberg lettuce crops. The cold is freezing the heads of the lettuce and affecting the quality and yield, Nolte said.

The price for a carton of lettuce in Yuma two weeks ago was $7 to $8. As of Monday, it costs around $20 per carton, he said.